In the operation of steam and boiler systems, it is often the case that steam which is available for use will be at a temperature much greater than is necessary or desired for a particular end use. In such cases, it is customary to utilize a desuperheater, by which a fluid, usually water is injected into the flowing stream of high temperature steam and subsequently mixed. Ideally, the injected fluid itself almost immediately turns to steam, serving to convert the incoming, high temperature steam to a somewhat larger volume of steam at a lower temperature, that is, the steam will have less superheat.
An earlier patent granted to Sanford S. Bowlus, U.S. Pat. No. 2,945,685, discloses an advantageous form of automatic desuperheater device, known as a variable orifice desuperheater. In the device of the Bowlus patent, incoming steam, traveling vertically upward through a desuperheater housing inlet, was arranged to lift against gravity a weighted valve element. The extent to which the valve element opened is automatically a function of the volume and velocity of the incoming steam.
Surrounding the weighted valve element is a small orifice communicating with a source of desuperheating water. When steam is flowing through the system the weighted valve element is lifted, resulting in a high velocity flow of the steam around the valve and an atomizing action of the steam on the surrounding water. The arrangement is such that, relatively independently of the volume of steam flow within reasonable limits, there will be an effective atomizing action of the steam upon the water. The amount of water injected into the desuperheater and combined with the incoming steam is controlled independently, as a function of steam temperature.
In basic principle, the variable orifice desuperheater of the Bowlus U.S. Pat. No. 2,945,685 is highly effective in operation. Thus, the present invention seeks to utilize the significant operative principles of the earlier Bowlus patent, while at the same time incorporating such principles into a substantially improved physical embodiment, which is more resistant to thermal fatigue than prior devices and at the same time less costly to produce and maintain. These advantages are achieved without sacrifice of performance and, indeed, with improvement in performance in certain respects.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.